Mg, Ca and Ba glutaratouranylates – Synthesis and structure

Article abstract of DOI:10.1016/j.poly.2017.11.031

Three novel uranyl coordination polymers were synthesized and structurally characterized by single crystal X-ray diffraction – [Mg(H₂O)₆][UO₂(glt)(Hglt)]₂·6H₂O (1), [Ca(H₂O)₄][UO₂(glt)(Hglt)]₂·4H₂O (2) and [Ba(H₂O)₅][UO₂(glt)(Hglt)]₂·2H₂O (3), where glt = C₅H₆O₄^2? (glutarate) and Hglt = C₅H₇O₄^? (hydroglutarate) anions. The structures of compounds 1–3 contain 1D [UO₂(glt)(Hglt)]^? units that belong to the AQ⁰²B⁰¹ (A = UO₂²⁺, Q⁰² = glt, B⁰¹ = Hglt) crystallochemical group. The different roles of alkaline earth R²⁺ cations in the structures and the flexibility of the glutarate anions account for the structural distinctions of 1–3. The diverse ways for the connection between the R²⁺ ions and the [UO₂(glt)(Hglt)]^? chains, the water content and the geometry of the uranyl-glutarate units present the main structural features of the new complexes. A comparative analysis based on Pauling's second rule of 1–3 and alkali glutaratouranylates has allowed an explanation of their structural dissimilarity.